The Irish version of the town Ballinagra should be "Baile an Ghrá", not "Baile na Grá" as depicted in the film.
In a scene where the senator (still in the US) is in a limousine, there are Ivory Coast flags flying from the car (orange, white and green, rather than the green, white and orange of the expected Irish flags). As this is exactly the kind of mistake a clueless wannabe-Irish politician might make, it might have been deliberate on the part of the film-makers.
Millie O'Dowd tells Marcy that the Japanese girl will be married tomorrow, yet two nights pass before Sean and Marcy drive by her outdoor wedding ceremony in Sean's boat.